Title: Fiber assembly employing photonic band-gap optical fiber.Abstract: A fiber assembly having at least one photonic band-gap fiber and opto-electronic devices coupled to the at least one fiber at either end. The opto-electronic devices serve as electrical-to-optical (EO) and optical-to-electrical (OE) converters and provide industry-standard electrical interfaces to respective electronic devices. The photonic band-gap fiber has a hollow core so that light travels through air rather than glass, thereby providing a number of advantages over glass-based optical fiber assemblies used to connect electronic devices. A bent optical fiber coupler for use in the fiber assembly is also disclosed. ...

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. Patent Application Ser. No. 61/130,482, filed on May 30, 2008, the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUND

The present invention relates generally to fiber assemblies, and in particular relates to fiber assemblies employing one or more photonic band-gap optical fibers.

2. Technical Background of the Invention

In the past, electronic devices communicated with other electronic devices via electrical connections. As the need to provide increasing speed and bandwidth to the electrical communication link, different types of high-speed, high-bandwidth electrical cables, such as coaxial cables, were developed.

Now, with the emerging higher speed standards for data and video transmission, such as 10 Gb/s Ethernet, infiniband, High-Definition Multimedia Interface (HDMI) and USB 3.0, there is an increasing the demand for the use of fiber optical cabling to communicate between electrical devices. The use of such cables requires electrical-to-optical (EO) and optical-electrical (OE) conversion at each end of the cable to retain the purely electrical interface to users at either end of the EO/OE system.

While convention optical fibers have larger bandwidths than electrical cables, they also have a number of shortcomings. A first shortcoming is that they have a solid glass core that creates one or more glass-air interfaces that cause reflections. Such reflections introduce optical loss, and also produce unwanted optical feedback. Glass-air interfaces also typically require coupling optics when interfacing the fiber with an opto-electronic device used to perform the EO or OE conversion.

A second shortcoming is that they are not particularly bend-intolerant—that is to say, they can be damaged and/or can cause significant attenuation of the optical signal traveling therethrough when subjected to severe bending, such as imparting a bend radius of 2″ or less. This is inconvenient when EO and OE devices are formed in or on circuit boards located in devices where interior space is at a premium. Conventional optical fibers and their connectors do not allow for readily accessing and connecting to a circuit board housed in the tight confines of most optical and opto-electronic devices because it requires introducing significant bending loss in the optical fibers. This is particularly true where the connection needs to be formed at a right angle with a sufficiently tight radius while maintaining both low loss and high reliability.

What is needed is a fiber assembly that provides a robust communication link between EO and OE devices that does not have the above-mentioned shortcomings associated with conventional optical fiber.

SUMMARY

A first aspect of the invention is a fiber assembly for optically connecting first and second electrical devices. The assembly includes at least one photonic band-gap optical fiber. First and second opto-electronic devices are respectively coupled to the at least one photonic band-gap optical fiber its respective ends, and configured to perform electrical-to-optical (EO) and/or optical-to-electrical (OE) conversion. First and second electrical interfaces are operably disposed relative to the first and second opto-electronic devices and are configured to provide respective industry-standard electrical connections to the first and second electrical devices.

A second aspect of the invention is a bent optical fiber coupler that includes upper and lower alignment members. The upper fiber alignment member has a concave surface and the lower fiber alignment member has a bottom surface defining a coupler output end, and a convex surface. The lower and upper fiber alignment members are arranged to form a first fiber guide channel defining a first coupler input/output (I/O) end, a channel end, and a central curve defined by said convex and concave surfaces. The coupler also includes at least one photonic band-gap optical fiber having an end portion with a proximal end face. At least a portion of the at least one photonic band-gap fiber is held within the first fiber guide channel so as to form a bend in the at least on photonic band-gap fiber corresponding to the central curve, and to position the fiber end face at or near the bottom surface of the lower fiber alignment member so as to define a second coupler I/O end.

A third aspect of the invention is a method of forming an optical coupler. The method includes providing at least one photonic band-gap optical fiber having an end portion with a proximal end face, and holding the at least one photonic band-gap optical fiber between respective concave and convex surfaces of upper and lower fiber alignment guides so as to form a bend in the at least one photonic band-gap optical fiber. In an example embodiment, the bend is a right-angle bend.

A fourth aspect of the invention is a method of optically connecting first and second electrical device. The method includes providing least one photonic band-gap optical fiber having a hollow core and first and second ends. The method also includes connecting first and second opto-electronic devices to the respective first and second ends of the at least one photonic band-gap optical fiber, wherein the first and second opto-electronic devices are configured to perform electrical-to-optical (EO) and/or optical-to-electrical (OE) conversion. The method further includes operably disposing first and second electrical interfaces relative to the first and second opto-electronic devices so as to provide respective electrical connections between the first and second opto-electronic devices and the first and second electrical devices.

Additional features and advantages of the invention will be set forth in the detailed description that follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description that follows, the claims, as well as the appended drawings. It is to be understood that both the foregoing general description and the following detailed description present exemplary embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the detailed description, serve to explain the principles and operations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the present invention are better understood when the following detailed description of the invention is read with reference to the accompanying drawings, in which:

FIG. 1 is a side view of a section of a photonic band-gap fiber;

FIG. 2 is a cross-sectional schematic view of the photonic band-gap fiber of FIG. 1 taken along the line 2-2;

FIG. 3 is a cross-sectional schematic view of two photonic band-gap structures having different pitches and hole sizes;

FIG. 4 are cross-sectional schematic views of an example method of fabricating the example photonic band-gap fibers used the present invention;

FIG. 5 is a close-up view of an end of a photonic band-gap fiber coupled to a light source, with the numerical aperture (NA) of the optical fiber being greater than that of the light source;

FIG. 6 is a schematic cross-sectional exploded view of an example bent optical fiber coupler according to the present invention that employs one or more photonic band-gap optical fibers;

FIG. 7 is similar to but is an unexploded cross-sectional view and also includes a strain-relief element at one of the input/output (I/O) ends and that also includes an opto-electronic device arranged at the other I/O end;

FIG. 8 is a schematic side view of a photonic band-gap optical fiber illustrating the concept of a right-angle bend in the form of a quarter-round bend in the fiber;

FIG. 9 is a schematic diagram of an opto-electronic assembly that includes the optical fiber coupler of the present invention;

FIG. 10 is similar to FIG. 9 and shows an example opto-electronic device in the form of a VSCEL assembly;

FIG. 11 is a close-up exploded view of the upper and lower alignment members showing a divider member arranged between the concave and convex surfaces to divide the curved fiber guide channel into multiple channels each including a row of photonic band-gap fibers;

FIG. 12A illustrates an example embodiment of the coupler in the process of being fabricated, showing lower alignment member and unbent photonic band-gap fiber positioned to have its end portion inserted into the optical fiber guide in the lower alignment member;

FIG. 12B shows the next step in the example fabrication process wherein the fiber has its end portion inserted into lower alignment member optical fiber guide with the fiber extending vertically therefrom;

FIG. 12C shows the next step in the example fabrication process wherein the fiber is bent to conform to the convex surface portion of the lower alignment member;

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